1. Field of the Invention
This invention relates to radiation detection. More particularly, the invention relates to a method and device for long-range, passive detection and localization of fissile material, with some particular applications in homeland security.
2. Description of the Related Art
The background to the present invention and related art is best understood by reference to Applicant's own prior work, including in particularly, U.S. Pat. No. 7,002,159 B2 (the '159) entitled “Boron Coated Straw Neutron Detector” which issued Feb. 21, 2006. The '159 patent is hereby incorporated by reference in its entirety, for all purposes, including, but not limited to, supplying background and enabling those skilled in the art to understand, make and use in Applicant's present invention.
Applicant's other issued patents and pending applications may also be relevant, including; (1) U.S. Pat. No. 5,573,747 entitled, “Method for Preparing a Physiological Isotonic Pet Radiopharmaceutical of 62CU; (2) U.S. Pat. No. 6,078,039 entitled, “Segmental Tube Array High Pressure Gas Proportional Detector for Nuclear Medicine Imaging”; (3) U.S. Pat. No. 6,264,597 entitled, “Intravascular Radiotherapy Employing a Safe Liquid Suspended Short-Lived Source”; (4) U.S. Pat. No. 6,483,114 D1 entitled, “Positron Camera”; (5) U.S. Pat. No. 6,486,468 entitled, “High Resolution, High Pressure Xenon Gamma Rays Spectroscopy Using Primary and Stimulated Light Emissions; (6) U.S. Pat. No. 7,078,704 entitled, “Cylindrical Ionization Detector with a Resistive Cathode and External Readout; (7) U.S. patent application Ser. No. 10/571,202, entitled, “Miniaturized 62Zn/62CU Generator for High Concentration and Clinical Deliveries of 62CU Kit Formulation for the Facile Preparation of Radiolabeled Cu-bis(thiosemicarbazone) Compound.” Each of these listed patents are hereby incorporated by reference in their entirety for all purposes.
There has been increasing interest in detecting nuclear materials for many years, especially since Sep. 11, 2001. Nuclear detection often uses neutron detection because neutrons can readily penetrate most materials. A common neutron detector is a tube of helium-3 (3He) gas linked to a power supply, with positively and negatively-charged plates or wires in the tubes. When a low-energy neutron passes through the tube, a helium-3 atom absorbs it, producing energetic charged particles that lose their energy by knocking electrons off other helium-3 atoms. Current neutron detectors, such as those using 3He tubes, have significant practical limitations, including high cost and substantial weight and bulkiness, and are dangerous in portable use due to the high pressure required. Additionally, helium-3 is scarce and it is thought there may not be enough available to support large scale use of these type tubes. Therefore, a compelling need has emerged for alternative detectors with more favorable characteristics.